Explanation of background of the present invention starts with a VANET without roadside units. As roadside units mostly serve as gateways to the Internet, such a VANET becomes a huge intranet, which is an isolated IP (Internet Protocol) network. Such kind of VANETs will be referred to as pure VANETs in this application.
The main issue of a pure VANET is its performance. First, the number of hops needed between two communicating end points can become excessively large. Second, a pure VANET can be disconnected if there are insufficient VANET vehicles on the street.
To understand this problem, consider the case wherein two VANET vehicles communicate with one another, with a highways distance of 300 km separating between them. Using directional antennas, distance between transmitting and receiving vehicles over a single hop can be as high as 2-6 km. Thus, the number of hops in the round trip between these two vehicles is between 100 and 300. If per hop delay is 5 msecs, the total round trip time between the two vehicles could be as high as 1500 msecs, which is unacceptable. Therefore, for a pure VANET to be practical, it is necessary to minimize per hop delay. Further, another way to tackle the latency problem is to minimize the number of hops between two communications end points.
Yet another major technical problem with a pure VANET is lack of centralized infrastructure. In a pure VANET, the entire network is comprised of VANET devices installed in VANET vehicles. Typically a VANET device is a telematics box with limited computing and communications capacity. There are no centralized servers, switches, routers, or other heavy-duty telecommunications gears, which are often deployed by carriers. The challenge is to enable network control and management functions such as routing, connection setup/tear-down, without these gears organized in a centralized infrastructure.
Therefore, a pure VANET is highly inadequate to provide telecommunication services such as mobile voice, mobile Internet, etc., which are routinely provided by carriers.
Second, the background of the present invention is explained with regard to optimal routing and incentives in VANET.
The wireless technology has now reached its theoretical limits (constrained by physics) that are impossible to surpass. The only way to further increase data speed is to shorten the transmission range and use smaller cells. Since the introduction of iPhones, the smartphone demand has skyrocketed. Thus, the demand for wireless mobile data bandwidth is ramping up at the time when the supply of bandwidth is hitting the ultimate bottleneck.
This problem is particularly acute for vehicle mobile Internet (VMI) services. All major automakers of the world have spent a large sum of money to develop telematics services in the past decade. With the increasing popularity of wireless data services, demand for in-vehicle data services is also rising. One major issue facing VMI services is the need for high data rates.
VMI services are different from data services for small handheld devices. For smartphones, the display size is usually small (3″-4″ display). However, for in-vehicle Internet services, the actual device could be multiple laptops (10″-20″ display), multiple smartphones, or in-vehicle Internet devices of all kinds. Thus, the data rate required for VMI is a lot more than the data rate required for a smartphone.
The data rate is especially large if multimedia and streaming applications are used in a car. For medium-quality video streaming, a minimum of 800 Kbps to 1.15 Mbps is needed. For live stream HDTV, the data rate requirement jumps to 8-10 Mbps. Thus, when there are multiple laptops streaming high-quality videos in the same vehicle, the bandwidth requirement can jump to 10-20 Mbps, which is not sustainable in today's 3G or 4G networks.
The 326 Mbps peak download speed from the LTE technology is misleading. This speed is only achievable near the cell center. If a terminal is at mid-range or a far distance from the cell center, the drop in peak data rate is large—the drop in data rate is exponential in distance. Further, as more bits are stuffed in each symbol, the rate is highly susceptible to interference from obstructing objects (glass buildings and elevators especially). Therefore, the traditional macro-cell architecture is no longer feasible if HDTV streaming is required in a car.
Therefore, the VANET architecture is almost assuredly needed even as carriers are touting 4G (LTE, WiMAX, HSPA+) technologies. No matter what will happen, due to the fundamental limits imposed by physics, the only way to provide HDTV and other high-bandwidth services in a vehicle is via a small-cell short-range transmission infrastructure. Since vehicles are mobile, the infrastructure has to be ad hoc—this means the VANET architecture.
The most common VANET architecture is based on the Wi-Fi technology. Currently, IEEE is in the process of standardizing the 802.11p (WAVE) technology based on this architecture.
In a VANET, there are two kinds of communication: vehicle-to-vehicle (V2V) and vehicle-to-roadside (V2R). The two major technical issues for VANET are: (a) high MAC (media access control) layer overheads in the ad hoc communication, and (2) inefficient routing.
In the current VANET technology, vehicles communicate with one another by tuning to the same channel. Since Wi-Fi is based on CSMA C/A (carrier sense multiple access collision avoidance) control scheme, a transmitter is allowed to send if it senses that the channel is unused. This can result in packet collisions. Such issues are called the hidden node problem, which includes two sub-problems: the hidden terminal problem and the hidden transmitter problem. There are two approaches to this problem: (1) explicit reservation, (2) and implicit reservation.
In the explicit reservation approach, a common method is to use RTS (request-to-send) and CTS (clear-to-send) signaling to reserve a packet/frame slot. Such a scheme may incur too much delay and is not suitable for real-time applications. Other explicit reservation schemes use a TDMA (time division multiplexing) method. One example is called STDMA (self-organizing TDMA) which is used in a commercial system called AIS (automatic identification system) for communications between ships.
In the implicit reservation approach, priority queuing is used. This is the approach adopted by IEEE 802.11p. The problem with such a scheme is that delay is unbounded.
No matter which scheme is used, excessive amount of time is wasted in control signaling. For most data applications, any RTT (round trip time) greater than 300 ms (milliseconds) is barely tolerable. For real-time applications such as voice conversations, RTT greater than 250 ms is impossible. Now, MAC layer control can add as much as 20-30 ms per hop in a VANET. If the a packet has to traverse 10 hops in a VANET, the delay incurred in the VANET is already 200-300 ms, making the VANET unsuitable as a high-quality internet medium.
To minimize the number of hops inside a VANET, it is necessary to allow more transmitters to send to the same receiver. This may cause packet collisions at the receiver if no reservation is made. Two issues arise from this approach. How to choose a proper receiver from a group of VANET nodes, and how to minimize packet collisions?
Another major technical issue for a VANET is that routing is inefficient and unreliable. The conventional shortest path routing does a poor job in an ad hoc network where the network topology can change rapidly. Often the computation to find the best path takes too much time, and the paths found remain problematic (having a long latency, for example). In addition, a single or multiple faults can disconnect a node easily.
A major business issue in VANET deployment is getting a critical mass of roadside access points. The present invention will also provide a method for incentivizing roadside merchants and residents to share their broadband bandwidth via access points.
For the easy reference, a VANET that is constructed in accordance with the present invention will be referred to as VINET (vehicle inter-network).
Third, the background of the invention is explained with regard to P2P mobile virtual network operator model and routing. In a VANET, free Wi-Fi bandwidths are available to for both V2V (vehicle to vehicle) and V2R (vehicle to roadside) data communications. A major application of VANET is VMI (vehicle mobile Internet), in which a user in the car connect to the Internet through a gateway which serves as the backhaul access point to the Internet. The VANET operator pays for the backhaul bandwidth, and the VANET vehicle owners pay for the Wi-Fi bandwidth within the VANET. In this case, the vehicle owners share the V2V bandwidth, and the vehicle owners and the VANET operator share the V2R bandwidth. The carriers have on contribution to the bandwidth in this setup
However, when the number of VANET vehicles on the street is too low, for example, at night or during the holidays, a VANET operator will enable a VANET vehicle to connect directly to a cellular carrier. At the writing of the present invention, no commercial VANET is operational, and often a carrier will offer VMI service to vehicle owners.
Fourth, the background of the invention is explained with respect to business scheme that can be realized with the present invention. Free-Air business model has numerous ways of monetizing the free services, among them, the primary and native is LBMA.
LBMA has been touted as the Holy Grail of advertising because of geo-targeting. These ads are given at a time when a consumer actually needs merchants' information or at a location where he welcomes the convenience of piggybacking on his intended trip.
The CTR (click through rate) for LBMA is about 10 times better than non-targeted ads. In a recent month-long trial by Chili's using Navteq's LocationPoint platform, the advertisers posted a click-through rate high of 2.49 percent—more than 13 times the 0.19 average of online banner ads, according to Forrester Research.
The Navteq trial found that of those consumers who clicked on location intelligent ads, 39 percent clicked through for additional details, including turn-by-turn or step-by-step directions to the advertised merchant's retail location. In Europe similar trials show 7 percent CTR and a 39 percent conversion to “click to map.”
Navteq adds: “The power of location-based advertising is creating a virtual storefront.” LBMA actually extends retailers' storefront a couple-mile radius around the location, essentially inviting the ad receiver to come in and transact.